Proposed web API attributes for moving objects & sensor data

[rjksmith]

Background

OGC Testbed-16 Full Motion Video to Moving Features work has highlighted the benefits of exporting embedded (in-band) video metadata to linked (out-of-band) files for web access using Web Video Map Tracks (WebVMT), including the need for a web API for moving objects & sensors.

Issue

Given that data for moving objects can be sampled and interpolated sufficiently to synchronise with video, how best should moving object & sensor data be accessed on the web?

Discussion

Which attributes would be:

• Valuable to know;
• Simple to calculate;
• Common to many use cases.

Moving Objects

A moving object is defined as an identified object associated with a sequence of timed geolocations.

Simple, common attributes for moving objects are:

1. Distance travelled;
2. Speed;
3. Heading.

Useful speed attributes may include:

• Ground speed;
• Indicated air speed - for flight control;
• True air speed - for navigation;
• Average speed during an interval.

Moving objects with accelerometers and gyroscopes can measure impacts and rotations. Are there sufficient use cases to justify their inclusion, given that these values may not be available for all instances, and are the calculations involved sufficiently lightweight for resource-limited devices?

Sensor Data

A sensor is defined as an identified object associated with a sequence of timed observations.

Simple, common attributes for sensor data are:

1. Type - e.g. number, string, boolean, object, array;
2. Numeric range - min & max (for number);
3. Measurement units - string;
4. Description - string (for discoverability).

Useful numeric attributes may include:

• Observed max;
• Observed min;
• Observed average during an interval.

Should guidance be given on preferred measurement units, e.g. SI units, or should this field be limited to a list of options? Should guidance be given on syntax for description, e.g. including keywords from a list of options?